This disclosure is directed to a thermal fluxmeter and particular mounting fixtures therefor. In determining the heat loss of certain structures, it is helpful to measure the heat flux from a specified point. To the degree that a measuring device is placed on the surface, it interferes, at least in theory, with the heat loss. That is, the measuring device itself may well function as an insulator and reduce the flux which is assayed in the measurement. On the other hand, it is necessary to contact a thermal fluxmeter against a surface area for obtaining the measurement. The degree and consistency of contact between the flux measuring device and the surface undergoing measurement may create error in the measurements. Accordingly, relatively brief but intimate and consistent contact between the sensitive area of the fluxmeter and the object undergoing tests helps immensely in obtaining quality data.
One mode of assisting this contact is to apply paste or heat conductive grease to an area before positioning a thermal fluxmeter against that area. As an aid to this, applying the thermal fluxmeter against the surface with a firm force helps get more consistent data. The heat flow is consistently "sampled". A firm force is helpful in the sense that there is more intimate surface contact between the test instrument and the surface of interest. This either reduces or eliminates the microvoids at the interface (under the fluxmeter) to obtain a more accurate representation of the metered surface. While one might state (in theory) that maximum force yields maximum accuracy, there is a point of diminishing return with increasing force.
This device enables a reasonable and steady force to be applied. The force is sufficiently high to minimize interspacial thermal resistance errors. This increases the repeatability of the apparatus by assuring that approximately the same force is applied on each use of the device. Moreover, it enables the device to be applied and removed (about one minute dwell time) so that distortion of the thermal flux by the test instrument is reduced. In the application of a thermal fluxmeter to a specified area, an initial transient stabilizes on heat saturation of the thin fluxmeter to enable a "settled" reading.
The present apparatus enables a thermal fluxmeter to be applied to a surface. The present apparatus includes a mounting fixture. In fact, alternate mounting fixtures are illustrated, thereby providing one device which can be used on flat surfaces and another device which finds suitable application on curved surfaces. The latter can be used on the sides of storage tanks, pressure vessels, pipe and the like.
This device applies a thermal fluxmeter to a surface with a force which is more or less stablilized. In this light, repetitive measurements can be implemented, thereby assuring reasonably accurate, repeatable data.
With the foregoing in view, the apparatus is briefly summarized as a hand held portable fixture with a handle suitable to be grasped. Further, the device includes a constant force spring which resists the application of the device so that loading is approximately consistant and substantially uniform from use to use. The apparatus thus enables the thermal fluxmeter to be held against the surface. Output data is obtained from the thermopiles in the thermal fluxmeter.